sandy wrote:

For a certain distribution, the measurement 12.1 is 1.5 standard deviations below the mean, and the measurement 17.5 is 3.0 standard deviations above the mean. What is the mean of the distribution?

A. 13.8

B. 13.9

C. 14.0

D. 14.1

E. 14.2

Another approach:

Let M = the mean

Let D = standard deviation

12.1 is 1.5 standard deviations below the meanSo,

M - 1.5D = 12.1 17.5 is 3.0 standard deviations above the meanSo,

M + 3D = 17.5We have the system:

M - 1.5D = 12.1M + 3D = 17.5Multiple both sides of the top equation by 2 to get:

2M - 3D = 24.2M + 3D = 17.5ADD the two equations to get: 3M = 41.7

Solve to get: M = 13.9

Answer: B

Cheers,

Brent

_________________

Brent Hanneson – Creator of greenlighttestprep.com

Sign up for my free GRE Question of the Day emails